Hammer drill attachment for electric motors



June 16, 1942.

E. N. WALTER HAMMER DRILL ATTACHMENT FOR ELECTRIC MOTORS Filed Sept. 3, 1940 19 v. C L I 2/ w l7 Q5 M Q62) IIIIIIIEEMIM w ill j 20 22 Mranton- Patented June 16, 1942 UNITED STATES PATENT OFFICE HAMMER DRILL ATTACHIVIENT FOR ELECTRIC MOTORS 4 Claims.

This invention relates to a hammer drill attachment for electric motors and like power units having a rotary driven element, and has as an object to provide an improved unitary assembly adapted for operative connection with the rotatably-driven element of such a power unit to convert such rotation into reciprocatory action for use in drilling, riveting, and similar hammering operations.

A further object of the invention is to provide an improved hammer attachment susceptible of convenient selective association with conventional rotary power units to facilitate the drilling of holes in masonry and similar emplacements.

A further object of the invention is to provide an improved hammer unit assembly arranged for convenient practical manipulation in power association with a conventional electric motor for the drilling of holes in masonry emplacements and so located as to be otherwise difficult of access.

A further object of the invention is to provide an improved unitary assembly of cooperating elements constituting a hammer drill attachment for electric power units.

A further object of the invention is to provide a hammer attachment for electric motors that is inexpensive of manufacture, light in weight, arranged for convenient operative association with conventional chuck members of electric motors, and which is efficient and durable in use.

My invention consists in the construction, arrangement, and combination of elements hereinafter set forth, pointed out in my claims, and illustrated by the accompanying drawing, in which- Figure 1 is a side elevation, largely in longitudinal section, of my improved attachment as assembled and operatively connected with the chuck element of an electric motor for practical use. Figure 2 is a bottom plan view of the attachment shown in Figure 1 when separated from its association with a power unit. Figure 3 is a cross section of the improvement taken on the indicated line 3-3 of Figure 1. Figure 4 is a fragmentary, detail section taken on the indicated line 44 of Figure 1. Figure 5 is a cross section taken on the indicated line 55 of Figure 1.

In the construction of the improvement as shown, the numeral I0 designates the principal frame or body member of the improvement, which frame is preferably formed of metal, in any suitable or desired manner, and comprises an elongated tubular portion having a substantially uniform cylindrical bore opening through its ends, spaced, parallel, longitudinal webs or ribs H extending transversely from one side of the tubular member along approximately one-half of the tubular member length to define a slot or channel, a handle grip l2 adjacent one end of the tubular member and extending radially thereof in closing relation across the slot between the ribs II, and a cylindrical, hollow boss [3 projecting from a midportion of the tubular member at one end of the ribs II and in axially-perpendicular relation with said tubular member.

The frame [0, and elements ll, l2, and [3 integrally associated therewith, constitutes a pistollike housing and support for the cooperating elements which comprise the power-transmitting portion of the hammer unit. Received and fitted for axial reciprocation within, and extending at one end beyond, that portion of the bore of the frame [0 remote from the handle [2, a plunger [4 is slidably disposed and is held against relative rotation and limited in the amount of its relative reciprocation by means of a threaded stud 15 which removably engages through a wall of the tubular frame member to position its inner end within a relatively short slot or keyway l6 recessed into an adjacent portion of said plunger. The end of the plunger l4 extending outwardly of and beyond the tubular frame member is fixed to, formed integrally with, or otherwise supports as an axial extension a chuck I1 adapted to receive and hold the shank 18 of a tool, such as a drill bit, thereby disposed in axial alignment with the plunger I4. The chuck Il may be of any specific construction and mechanical arrangement suited to its purpose, and is shown in the drawing as of a type to slidably receive and frictionally hold the taper shank I8, a suitable slot [9 being formed transversely of the chuck to facilitate removal of the tool shank, when desired. As will be apparent, the plunger I4 is normally held within and in limited sliding relation with the tubular member of the frame [0 in a manner to position the chuck H in somewhat spaced relation with the adjacent end of said frame member, removal of the plunger l4 and chuck H from the frame member being made possible by the removable character of the threaded stud l5.

In end-abutting relation with the end portion of the plunger I l housed within the tubular member of the frame iii, a cylindrical impact element 28 is closely fitted and slidably disposed for axial reciprocation within the bore of the tubular frame member, and said impact element is formed with a radial fin 2! which is fixed to or formed integrally with said impact element 20 and extends beyond the outer periphery of said impact element to lie within and for reciprocation between the frame ribs II. The impact element 2% has a length less than that of the tubular frame member which is unoccupied by the plunger I l, and said impact element is urged into end contact with said plunger by means of an expansive coil spring 22 disposed in the bore of the tubular frame member to bear at one end against the free end of the impact element and at its other end against a threaded plug 23 which is adjustably engaged with threads formed in the handle end of the tubular frame member bore, said plug 23 thus acting to close the handle end of said bore and also serving as means whereby the expansive tension of the spring 22 may be regulated and adjusted. As will be obvious, the expansive force of the spring 22 acts to urge'the impact element Ell-against the adjacent end of the plunger 14 and thereby maintain said plunger at its limit of'extension-outwardly of the frame it determined by engagement of the stud 15 within the slot or keyway I6, and'the fin 2| is so shaped and associated with the elementZt asto-positionastraight end margin of said fin disposed radially of the impact element 23 within the cylindrical boss 43 aheadoi" the juncticn'of said boss with the ribs H when the plunger E4 is at the'limit'of i-tsextension outwardlyoi the-frame it, -as is shown in Figure '1.

A fitting 26 is formed asa-closure member for and to threadedly or otherwise remova'bly -coin fixed relation with one end of a shaft -23 which "is journaled within -the-b0re"0i the fitting 24am extends a considerable distance outwardly beyond the outer end of said fitting. The cam -25 is thus disposed for peripheral engagement against the straight, radially-disposed endof-the fin 2| so that assaid cam is rotated'in the proper direction, the lobes of the cam alternately retract the impaot elenientl fs againstthe'pressure of the'spring 222 and release said impact element for impact effect on the -plunger M deriving from the expansive force ofsaid'spring. The outer or free end of the shaft 25 is of a-size and specific shape suitable for engagement within and operative association with a clamp-type chuck carried by the driven shaft of an electric -motor-or an equivalent prime mover, such a chuck being conventionally indicated at 2'3 and being-commonly found as an element of portable electric motors manufactured for general utility purposes. Since the hammer attachment constituting the subject matter of the instant invention is susceptible of use with'motors of various sizes and specific constructions, it is believed that no showing or description of the specific power unit and associated chuck constructionis necessary or desirable to a complete and competent understanding of the invention.

Since many changes, variations, and modifications in the specific form, construction, and arrangement of the elements shown and described may be had without departing from the spirit of my invention, I wish to be understood as being limited solely by the scope of the appended claims, rather than by any details of the illustrative showing and foregoing description.

I claim as my invention- 1. A hammer attachment for operative association with electric motors and equivalent rotary power units, comprising an elongate frame formed with a longitudinal bore opening through both of its ends, a handle on and disposed radially of one end of said frame, a slot communicating with and radially of said bore through the handled portion of said frame, a plunger mounted for limited reciprocation within and extended at one end outwardly beyond the end of said bore remote from said handle, tool-supporting means associated with the outwardlyextending end of said plunger, an impact element freely reciprocable in said bore for impact eifect on said plunger, a radial fin on said impact element slidably engaging in said slot, a 'plug 'threadedl'y engaging the end of said bore adjacent said handle, spring means within said bore-engaging between said plug-and the adjacent end of "said impact-element tourgethelat- 'ter into-end engagement 'against'said plunger, a rotatable cammarriedjby said frame for -engagement with one endof said fin to retract'said impact element against the pressure of said spring means, and means for operatively connecting said cam with the -rctatably'-driven element of a-power unit.

2. Ahammer attachment for selectivecperative association withan electricmotor' orequivalent rotary'power means, said attachment comprising an elongate frame-formed "with'a straight, longitudinal bore opening through 'its ends, a handle adjacent and radially of one end of said frame a slot communicating with and 'radially of said 'bore through the handled portion of saidframe, a plunger mounted for reciprocation in the end of said bore remote fromsaid handle, tool-supporting means carried'by said 'plungerexteriorly of said frame, an-impact 'ele- 'ment freely reciprocable in saidbore'for im'pact eifect on said plunger, a radial fin-on said impact element slidably received in said slot, a -shoulder-on the-end of said fin adjacent said plunger, -a plug threadedly engaging within the -end'o'f'- said boreadjacent said handle,- expansive spring means --in said bore between said'plug and impact-element -to normally urge the latter into end engagement with said plunger, cam-means rotatablycarried by said frame for engagement against the-shoulder'cf said fin to retractsaid impact element against the pressure of said spring, and means for operatively connecting-said cam with the rotatably-driven element of -a='power unit.

3. -A hammer attachment for"selective association with the rotatably-driven element of an electric motor "or equivalent power means, said attachment comprising an elongate frame formedwitha longitudinal bore opening through its opposite endsanda handle on and 'dispose'd radially of one-of its ends, a plunger 'mou'nted for limited reciprocation within the end portion of said boreremote from said handle, tool-supporting means carried by said plungerexteriorly of said frame, a longitudinal slide bearing-coinmunicating radially with 'said bore rear-wairdly of said plunger and -opening through the liandled end of said frame, an impact ele'ment formed with 'a radial fin engaging said slide bearing' mounted for free reciprocation in said bore and for impact effect on said plunger, "a

plug threadedly engaging within said bore adjacent said handle, an expansive coil spring in said bore between said plug and the adjacent end of said impact element to normally urge the latter into end engagement with said plunger, a shaft rotatably carried adjacent the forward end of said slide bearing in axially-perpendicular relation with said bore and radially thereof in substantial alignment with said handle, means for connecting the outer end of said shaft with a rotatably-driven power unit, and a cam on the inner end of said shaft for engagement with the forward end of said fin, whereby rotation of said cam acts to retract said impact element against the pressure of said spring.

4. In an attachment of the character described having an elongate frame, a bore longitudinally of and opening through the ends of said frame, a pistol-type handle on and radially of one end of said frame, and a tool-supporting plunger mounted for limited reciprocation in the end of said bore remote from said handle, a cylindrical chamber in a midportion of said frame and disposed with its axis radially of said bore and substantially parallel with said handle, a slide bearing opening longitudinally between said chamber and the handled end of said frame in communication with said bore, an impact element mounted for reciprocation in said bore, a radial fin on said impact element engaging within said slide bearing, a shoulder on the forward end of said fin and normally disposed within said chamber, a plug threadedly closing the handled end of said bore, an expansive coil spring engaging between said plug and the adjacent end of said impact element to normally urge the latter into end engagement with said plunger, a shaft mounted for rotation axially of said chamber, means for connecting the outer end of said shaft with the rotatably-driven element of a power unit, and a cam fixed to the inner end of said shaft within said chamber for bearing engagement against the shoulder of said fin and consequent retraction of said impact element against the pressure of said spring.

EARL N. WALTER. 

